This invention relates to towing vehicles and more particularly to an extendible ramp on the front of a wheel lift tow bar for providing support to the front of the wheels or tires of a vehicle being towed.
Because of the large amount of plastic material used on the front and rear portions and bumpers of recent model automobiles, developments in the art of lifting and towing disabled vehicles by a towing vehicle have been directed toward what is known in the art as "wheel lift" devices, which engage and lift the front or rear tires of a disabled vehicle. Examples of towing apparatus incorporating such devices are illustrated in Wagner U.S. Pat. No. 3,182,829; Bubik U.S. Pat. No. 3,897,879; Cannon et al U.S. Pat. No. 4,451,193; Brown U.S. Pat. No. 4,473,334; Porter et al U.S. Pat. No. 4,573,857; Hamman U.S. Pat. No. 4,634,337; Bubik U.S. Pat. No. 4,637,623 and Holmes U.S. Pat. No. 4,679,978. As disclosed in each of these patents the tires of a disabled vehicle are disposed within the well of some form of cradle, the cradle having members which engage and support the front and rear of the tires carried therein.
The wheel supporting cradles generally have a fork of a substantially U-shaped configuration in plan, the legs of the cradle opening either inwardly, outwardly or rearwardly. In the latter instance the open position is closed by a retaining member subsequent to the tire being disposed within the well, the retaining member engaging the rear of the tire. In the former cases, the rear of the tire is engaged by an arm, commonly known in the art as an "L" arm since it has that configuration, and such arm may have an upstanding arcuate contour conforming somewhat to the shape of the tire so as to provide greater support by the larger surface contact with the tire. Examples of the former "L" arm configurations are illustrated in at least the aforesaid Porter et al and Holmes patent, while examples of the latter "L" arm configurations are illustrated in at least Wagner and the Bubik '623 patents.
The front of the tire generally merely rests on a ramp either formed on the front leg of the U-shaped cradle, as in Cannon et al and Porter et al, or formed on the rear of a laterally extending cross arm or tow bar which carries the "L" arms at its extremities, such as in Bubik '623 and Holmes. In Wagner, both the front and rear support for the tires is provided by spaced apart arcuate shaped plates or feet which are connected together by chains so that both the front and rear of the tire is engaged by the greater surface contact provided by these contoured feet. However, in Wagner the feet on both sides of the vehicle are carried by a respective arm depending downwardly from a frame supported above the vehicle to be towed, and the entire wheel lift apparatus is difficult to utilize effectively. This is one reason the art has developed in the direction of engaging the tires with a wheel lift device which enters from beneath the disabled vehicle.
When a disabled vehicle is being towed, it is highly desirable that the tires rest securely within the cradle so that the momentum of the disabled vehicle does not result in the tires rolling and disengaging from the cradle when the towing vehicle accelerates or stops. On acceleration, the disabled vehicle and the tires tend to surge rearwardly, but upon stopping of the towing vehicle, the disabled vehicle and the tires tend to surge forwardly. Accordingly, it is highly desirable to have enlarged wheel engaging feet at the front and rear of the cradle.
One of the problems presented when engaging the tires from beneath the vehicle is that modern automobiles have a low configuration, that is, they are built low to the ground and the bodies thereof have low ground clearance and small clearance between the tire wells and the tires. Thus, if the cradle has enlarged feet, the low clearance prevents the feet from entering beneath the automobile from, for example, the front of the vehicle. If a large foot is desirable to support the front of the tire of the disabled vehicle, then the prior art, as exemplified by the aforesaid Porter et al patent, has not utilized a foot at the rear of the tire but has provided means for rotating the rear support of the cradle outwardly from beneath the vehicle. However, even here if the disabled vehicle has a very low ground clearance at the front, the upstanding foot will not slip beneath the body of the vehicle into the tire engaging position. If a large foot is desired to support the rear of the disabled tire, the foot may be rotated inwardly from the outboard side of the vehicle, as exemplified by the Bubik ' 623 patent. However, as illustrated in that patent, the front support is merely a ramp on the cross bar or the like since a large foot for supporting the front of the tire will not enter beneath the low ground clearance front end of late model vehicles.